const fs = require('fs')
const timeroutScheduled = Date.now()
setTimeout(() => {
  const delay = Date.now() - timeroutScheduled
  console.log(`${delay} was have passed since I was scheduled`)
}, 100)

fs.readFile('./file.js', (err, data) => {
  const startCallback = Date.now()
  // 使用while循环阻塞10ms
  while(Date.now() - startCallback < 10) {
    // do nothing
  }
})
